CHAP. VII. FOSSIL BOTANY. 313 



1. From the earliest secondary rocks to the upper- 

 most beds of the coal-measures. 



2. The new red sandstone series. 



3. From the lowest beds of the oolitic series to the 

 chalk inclusive. 



4. The beds above the chalk. 



Judging from analogy, from the characters and rela- 

 tive proportions of the species in different classes, the tem- 

 perature of those parts in which the plants of the first 

 period were growing must have been both hotter and 

 moister than the climates in any part of the earth at 

 present. It has been plausibly conjectured that the at- 

 mosphere was more charged with carbonic acid at those 

 early periods of our planet's history, when gigantic 

 species of cryptogamic plants formed the main feature 

 of its vegetation. The abundance of reptiles, also, 

 without any Mammalia during the same epoch, appears 

 favourable to this supposition. Since the fossil plants, 

 which have been found in the arctic regions, are 

 analogous to those which now grow in tropical islands, 

 it seems likely, that not only must they have enjoyed a 

 higher temperature, but also a more equable diffusion 

 of light than those regions now possess. Speculations 

 of this description, imperfect as they confessedly are at 

 present, may one day lead to the most important re- 

 sults, and may teach us many truths respecting the 

 earliest conditions of our planet, which the science of 

 astronomy could never have suggested. And surely no 

 one ought to consider such inquiries too bold for our 

 limited faculties, needless for our present, or dangerous 

 for our future welfare. No naturalist, desirous of know- 

 ing the truth, can be so weak as to fancy that any 

 search into the works of God, or any contemplation 

 of the wonders of his creation, can interfere with the 

 lessons he has taught us in his revealed and written word. 

 The commentator who wishes us to pay attention to 

 his interpretations of the sacred text, must not pro- 

 ceed upon the supposition that there has been any thing 

 written in the Bible for our learning, which can possibly 



